Generally, electric power generation/hydrogen production combination plants that operate to concurrently generate electric power and produce hydrogen are known (See, inter alia, Jpn. Pat. Appln. Laid-Open Publication No. 2004-224661).
Such a known electric power generation/hydrogen production combination plant will be described by referring to FIG. 5.
As shown in FIG. 5, the steam produced from a steam generator 1 of an electric power generation system 22, which may typically be a boiling water reactor, is supplied to a high pressure turbine 24 by way of a main steam pipe 15 to drive the high pressure turbine 24 to rotate and then led to a low pressure turbine 26 to drive by turn the low pressure turbine 26 to rotate in order to drive a generator 3 to rotate and generate electric power.
The steam that has worked in the high pressure and low pressure turbines 24, 26 is condensed back to liquid water by a condenser 4 and its pressure is raised by a condenser pump 5. Then, the water is heated by a low-pressure feed water heater 6 and its pressure is raised further by a feed water pump 7. Thereafter, the water is heated by a high-pressure feed water heater 2 and returned to the steam generator 1 by a feed water pipe 18 to circulate. In actual plant, the some high-pressure feed water heaters 2, the some condenser pumps 5, the some low-pressure feed water heaters 6 and the some feed water pumps 7 are arranged, according to the size of plant. The feed water heaters 2, 6 are arranged upstream and downstream relative to the feed water pump 7 to heat feed water.
The steam that goes out of the high-pressure turbine 24 is partly led to an intermediate heat exchanger 8 by way of heating inlet pipe 16 of intermediate heat exchanger 8. As the intermediate heat exchanger 8 operates to exchange heat, heat is transferred by way of an intermediate loop 19. The heat is then used to heat a reformer 9 for producing hydrogen in hydrogen production plant 23.
On the other hand, the steam that is used to exchange heat in the intermediate heat exchanger 8 is led to mixture gas preheater 10 by way of heating outlet pipe 17 of intermediate heat exchanger 8. It is then used to exchange heat in the mixture gas preheater 10 and subsequently led to the low-pressure turbine 26 to drive the low-pressure turbine 26 along with the steam directly transferred from the high pressure turbine 24.
In the hydrogen production plant 23, the raw material (mixture gas of methanol, ethanol or dimethylether and steam) is heated by the mixture gas preheater 10 and processed to produce hydrogen by the reformer 9. Since the gas generated in the reformer 9 contains gaseous substances other than hydrogen, only hydrogen is separated by a hydrogen separator 14.
In the above-described known electric power generation/hydrogen production combination plant, the heat of the steam produced by the steam generator 1 of the electric power generation system, is transmitted to the intermediate loop 19 by way of the intermediate heat exchanger 8. When heating the reformer 9 of the hydrogen generation plant 23 by way of the intermediate loop 19, it is necessary to efficiently transmit heat in the reformer 9 in order to utilize steam for power generation as much as possible. For this purpose, it is effective to use water having a large specific heat as thermal medium for the intermediate loop 19 and exploits the heat produced when such water is condensed.
As an example, if the thermal conductivity of saturated steam and that of superheated steam are compared at 250° C., the amount of heat that is generated when 1 kg of saturated steam is condensed is 1,715 kJ, whereas the amount of heat that is generated by 1 kg of superheated steam as a result of a temperature change is only about 1,340 kJ if the temperature change is a very large fall of temperature from 800° C. to 250° C.
However, collection of waste heat is not considered sufficiently for known electric power generation/hydrogen production combination plants. While some known electric power generation/hydrogen production combination plants are equipped with a thermal medium circulation means, no established specific means is available to date for the purpose of transmission of heat.
If the steam generated in a steam generation plant is saturated steam as in the case of light water nuclear reactors (including boiling water reactors and pressurized water reactors) that are used in the commercial nuclear power generation plants and it is used for heating in the intermediate heat exchanger, the steam is condensed to become liquid water without fail.
However, in known electric power generation/hydrogen production combination plants, the water produced by condensation in intermediate heat exchangers is not considered properly and the heating outlet pipes of intermediate heat exchangers are connected to the respective turbine inlets. With this arrangement, the water produced by condensation in the intermediate heat exchangers is forced to flow into the turbines to consequently give rise to problems including a reduced operation efficiency of the turbines and erosion of the internal structures of the turbines.
Additionally, if the steam generated in the steam generation plant is superheated steam as in the case of fast-breeder reactors and high temperature gas-cooled reactor and even in the case of the boilers of thermal power plants, which also produce superheated steam, it is effective to utilize the heat produced as a result of condensation in the intermediate heat exchangers when utilizing steam for power generation as much as possible. In such situations again, liquid water is produced by condensation to consequently give rise to problems including a reduced operation efficiency of the turbines and erosion of the internal structures of the turbines when the water produced by condensation is led to the turbines.